6f99a27886
This implements RFC 39. Omitted lifetimes in return values will now be
inferred to more useful defaults, and an error is reported if a lifetime
in a return type is omitted and one of the two lifetime elision rules
does not specify what it should be.
This primarily breaks two uncommon code patterns. The first is this:
unsafe fn get_foo_out_of_thin_air() -> &Foo {
...
}
This should be changed to:
unsafe fn get_foo_out_of_thin_air() -> &'static Foo {
...
}
The second pattern that needs to be changed is this:
enum MaybeBorrowed<'a> {
Borrowed(&'a str),
Owned(String),
}
fn foo() -> MaybeBorrowed {
Owned(format!("hello world"))
}
Change code like this to:
enum MaybeBorrowed<'a> {
Borrowed(&'a str),
Owned(String),
}
fn foo() -> MaybeBorrowed<'static> {
Owned(format!("hello world"))
}
Closes #15552.
[breaking-change]
72 lines
1.8 KiB
Rust
72 lines
1.8 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::rc::Rc;
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struct DerefWrapper<X, Y> {
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x: X,
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y: Y
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}
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impl<X, Y> DerefWrapper<X, Y> {
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fn get_x(self) -> X {
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self.x
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}
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}
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impl<X, Y> Deref<Y> for DerefWrapper<X, Y> {
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fn deref(&self) -> &Y {
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&self.y
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}
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}
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mod priv_test {
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pub struct DerefWrapperHideX<X, Y> {
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x: X,
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pub y: Y
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}
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impl<X, Y> DerefWrapperHideX<X, Y> {
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pub fn new(x: X, y: Y) -> DerefWrapperHideX<X, Y> {
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DerefWrapperHideX {
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x: x,
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y: y
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}
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}
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}
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impl<X, Y> Deref<Y> for DerefWrapperHideX<X, Y> {
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fn deref(&self) -> &Y {
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&self.y
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}
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}
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}
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pub fn main() {
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let nested = DerefWrapper {x: true, y: DerefWrapper {x: 0i, y: 1i}};
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// Use the first field that you can find.
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assert_eq!(nested.x, true);
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assert_eq!((*nested).x, 0);
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// Same for methods, even though there are multiple
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// candidates (at different nesting levels).
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assert_eq!(nested.get_x(), true);
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assert_eq!((*nested).get_x(), 0);
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// Also go through multiple levels of indirection.
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assert_eq!(Rc::new(nested).x, true);
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let nested_priv = priv_test::DerefWrapperHideX::new(true, DerefWrapper {x: 0i, y: 1i});
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// FIXME(eddyb) #12808 should skip private fields.
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// assert_eq!(nested_priv.x, 0);
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assert_eq!((*nested_priv).x, 0);
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}
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